Thanks for the response...
Why would you want to go through all the trouble of building this?
GPU rigs are fine with open air. I mine in a tropical country where ambient temp is higher than average. I have a small 39-GPU rig farm and run them at around 65 degrees using simple fucking fans. None of my GPUs have died. Been mining for a year now. ROI is real.
For once I am in a closed garage, so using fans will no exhaust the heat, at all.
Using fans in a closed spaced is mimicking an oven, that is why i need to vent to the outside.
If you'd take the time to run the numbers you'd probably see that a 500-1000cfm grow room fan with some 4 or 6" duct work would do you just fine.
great idea, just a concern, what if the grow fan fails, any tips to avoid damage to the cards
Temperature sensor connected to a rpi with a relay switch connected to another in-line fan? There are a lot of possible solutions. But you're trying to find a solution for unknown variables. You need to run the thermal transfer calculations.